delta-20-cyano-pregnene compounds and process for preparing them



Patented July 3, 1951 UNITED STATES PATENT (JFFl-CE A '2'o-oYnNo-PR GNENE COMPOUNDS AND PROCESS OR PREPARING THEM Lewis Hastings Sarett, Princeton, N. J., assignor to Merck 8506:, Inc., Rahway, N. J a corporation of New Jersey No Drawing.

Original application October 7,

1947, Serial No. 778,465. Divided and this application September 22,1948, Serial No. 50,668

cyano-pregnene compounds herein described 15 can be converted to the corresponding 17(00- hydroxy-20-keto-pregnane compounds according to the procedure outlined on the following page and described in detail in said co-pending applications.

CH: CH3

CH3 CH/QCN CH3 :0 CH3 p p OH HON Dehydrating agent 20-ketone-pregnane 20-hydroxy-20-cyano-20-pregnane The (a)-hydroxy groupings in the compounds configuration as that present in many of the naturally-occurring adrenal hormones. This is of special interest in the preparation of pregnene-4-diol 17(a),'21-trione-3,11,20-(commonly known as Kendalls Compound E), and its 21- acyl derivatives. These compounds are important as adrenal hormonesor in therapy requir- 5*Claims. (Cl. 260--'397.3)

ing adrenal hormone type compounds. They are further useful in the synthesis of similar hormones and compounds.

According to the present invention, 20-ketopregnane compounds are treated with hydrogen cyanide or one of its salts to produce the corresponding 20-hydroxy-20-cyano-pregnane compound. This product is reacted with a dehydrating agent to produce the corresponding A -cyano-pregnene, which is then reacted with an oxidizing agent and the intermediate product hydrolyzed to produce the corresponding, 17(00- hydroxy 20 keto-pregnane compound. The 17-hydroxy group, introduced according to this novelmethod; is obtainedi surprisingly enough} in only vone=isomeric form, namely. the a'Ol' nat-' ural configuration.

These reactions may 'be chemically represented 20 in the case of 20- keto pregnane asfollows-:"

Cap OH} g (1) Oxidizing agent (2)"H'ydrolysis A -20-cyaumpregnene For purposes of this application the configura thus obtained, have the same stereochemical 40 t representedby the'notation y y* is-to be understood-to represent'theconfigur'ation present in the" naturally occurring adrenal compounds;

The preferred class of startingmaterials' utilized in practicing the present invention'fiare 2 0- I keto-pregnanes whichtcont'a'in" free or esterifle'd hydroxy g-roupings in the :mo'lecule', and whichmay also contain keto-groupingst. These' pre ferred starting materials may be represented by the following generic formula:

wherein Ru and Rs are radicals selected from the class which consists of hydroxy radicals, 5

acyloxy radicals and hydrogen and R2 is a radical selected from the class which consists of keto radicals and hydrogen.

Examples of this preferred class of starting materials are: 3(a)-hydroxy-11,20-diketopregnane, 3-acetoxy-11,20-diketo-pregnane, 3-benzoxy-l1,20-diketo-pregnane, 3 (a) -hydroxy-11,20- diketo F 21 hydroxy-pregnane, 3(a) -hydroxy- 11,20 diketo-2l-acetoxy-pregnane, 3(a), 2l-diacetoXy-11,20-diketo-pregnane, and the like.

In carrying out my improved process, I ordinarily react a starting material of the above class with hydrogen cyanide, or one of its salts, preferably in solution in a lower aliphatic alcohol. When the resulting C- cyanhydrin contains free primary or secondary hydroxyl groupings, these may be protected, prior to the dehydration reaction, by conversion to the corresponding-acyloxy radicals. This is accomplished by reacting said cyanhydrin 'With an acylating agent, such as a lower aliphatic acid anhydride. Alternatively, a secondary hydroxyl group may be protected by oxidation to a ketone, since the C-20 cyanhydrin grouping is stable to this treatment. It is ordinarily preferred to conduct this oxidation reaction utilizing chromic acidas the oxidizing agent.

The dehydration reaction is best carried out by treating the cyanhydrin, after acylation or oxidation of any free hydroxyl groupings which may be present, with a dehydrating agent, such as phosphorus oxychloride. This reaction is ordinarily carried out in solution in a substantially anhydrous organic solvent, such as pyridine.

Moreover, the 20-hydroxy-20-cyano-pregnane compounds are stable to oxidizing agents. This unexpected property makes it possible to react 3,20 dihydroxy-20-cyano-pregnane compounds with oxidizing agents, such as chromic acid, to produce directly the corresponding 3-keto-20- hydroxy-20-cyano-pregnane compound.

The following examples illustrate methods of carrying out the present invention, but it is to be understood that these examples are given by way of illustration and not of limitation.

Example 1 CH3 7 CH;

CH, CH] ON on, 5 i OH HON -b CEO; i0)

3i CH3 CH1 (lg GN -oN CHI P 0 O1: gPyridine 7O A solution of 1.80 g. of 3(a) hydroxy -1l,20- diketopregnane (compound 1 above), which can be prepared as described by von Euw, Lardon and Reichstein in Helv. Chim. Acta 27, 821 (1944), in a mixture of 25 cc. of alcohol and 6.4 cc. of acetic acid at 0 C. is treated with 6.0 g. of potassium cyanide. The solution is allowed to warm to room temperature and after three hours is diluted with water and filtered. The wet crude cyanhydrin is dissolved in ethyl acetate and the extract washed with water. Crystallization then gives approximately 1.5 g. of 3(a),20-dihydroxy-20-cyano-l1- keto-pregnane (compound 2).

To a solution of 1.4 g..of 3(a),20-dihydroxy- 20-cyano-ll-keto-pregnane in 70 cc. of acetic acid is added at 16 C. a solution of 0.9 g. of chromic acid in 7 cc. of acetic acid. At the end of one hour, water is added, the crystalline precipitate filtered and recrystallized from ethyl acetate to produce approximately 0.93 g. of 3,11- diketo 20 hydroxy 20 cyano pregnane (compound 3), dec. 1'70-180 C.

About 0.60 cc. of phosphorus oxychloride is added to a solution containing 2.0 g. of 3,11- diketo-20-hydroxy-20-cyano-pregnane dissolved in 6.7 'cc. of pyridine. After standing at room temperature for 24 hours, the solutionis poured into water and dilute hydrochloric acid, extracted proximately 300 mg. of. A -3',11.-diketo'-20-cyanopregnene (compound-,4); M. P. 222-223" C.

tratedeto dryness. The'crudeiproduct, after ciao mato'graphy gives one main constituent, namely Example 2 OH! CH3 CH5 7 CHqOAc omom CHzOAc (5:0 CN CN 0 0 a 0H OH HON Grog IEIO- OH o=\/ H s) H H CH: CH: POO] QHaOH CHQOAC Pyridine --CN CN Aqueous GHaOH A solution of 2.0 g. of 3(a) -hydroxy-'21- acetoxy-11,20-diketo-pregnane (compound 8), which can be prepared as described byvon Euw, Lardon and Reichstein, Helv. Chim-.-Acta 27.; 1287- (1944), is treated in a mixture of cc. of alcohol and 6.4 cc. of acetic acid at 0 C. with 6.0 g. of potassium cyanide. The solution is allowedto warm to room temperature and after 3 hours is diluted with water. The addition of a large volume of water to the alcohol-hydrogen cyanide mixture precipitates a gum which is extracted with chloroform or ethyl acetate. The extract is washed with water, and evaporated to small volume under reduced pressure. Thecrystalline precipitate'(l.3 g.) consists of3(a),20-dihydr'oxy-20- cyano-Zl-acetoxy-ll' keto-pregnane (compound 9); dec. I-185 C. 4

CH3 on. =0

HCN-

AeO- I I Ac0 0.40 00. of phosphorus oxych-lorideis addedtoa solution containing about 950 mg. of 3,11-diketo 20 hydroxy- 20 cyano 21 acetoxy pregnane dissolved in 3 cc. of pyridine. After.

standing at room temperature for 24-hours,- the; solution is poured into'water and, dilute hydro chloric acid, extracted with benzeneand-concenered by filtration. Recrystallization of this ma-v terial from ethyl acetate gives substantially pure A -3,11-diketo-20-cyano 21 hydroxy-pregnene- (compound 20) M. P. 263-265 C.

Example 3 CH3 CH3 CH3 CN 011;. CH; 1 one 0 0 OH x Pyridine H (17) (18) About 1.70 g. of 3(a) -acetoxy11,20-diketopregnane (compound 16) which can be prepared as shown by von Euw, Lardon and Reichstein in Helv. Chim. Acta 27, 821 (1944) is dissolved in a mixture of 25 cc. of alcohol and 6.4 cc. of acetic acid and the solution is treated at 0 C. with 6.0 g. of potassium cyanide. The solution is allowed to warm to room temperature and after three hours is diluted with water and the material which precipitates recovered by filtration. The 3(a) acetoxy-20-hydroxy 20 cyano 11 ketopregnane (compound 17), thusobtained, may be purified by recrystallization from ethyl acetate.

It decomposes at about 221-223 C. Yield approximately of theory.

To a solution of 293 mg. of.3 (a) -acetoXy-20hydioxye20-cyano-ll-keto-pregnane in 1.0 cc. ofdry pyridine is added 0.10 cc. of phosphorus oxychloride. After standing at room temperature for 24 hours, the solution is poured into water and dilute hydrochloric acid, extracted with benzene and the benzene extract concentrated to dryness. The crystalline residue consists of a mixture of unsaturated nitriles which may be separated chromatographically to produce A -3(a)-acetoxy-11-keto-20-cyano-pregnene (compound 18);

ture is extracted with benzene and the benzene extract is evaporated to produce approximately 2.0 g. of an oil. This oil is subjected to chromatographic separation and the portions which are eluted, employing petroleum ether-ether mixtures, are combined to produce approximately 1.84 g. of crude A 3(a.) ,21-diacetoxy-11-keto- 20-cyano-pregnene which is obtained as an oil.

This oil is saponitfied by dissolving in a mixture of 10 cc. of benzene and 10 cc. of 1.1 N methanolic M. P. 194195 C. potassium hydroxide. After 10 minutes the solu- Emample 4 CH] CH] CH3 CH OAc CHgOAc CHIOAC =0 =0 -oN Acetic anhydtide HON 0H Pym! AcO A00 CHzOAc OHQOH y i CN ON 2. KOH omen Acetic anhydtide Pyridine HO 3(a) -hydroxy-11,20-diketo 21 acetoxy-pregnane (compound 22) is treated with excess pyridine-acetic anhydride and the mixture warmed on the steam bath for approximately 10 minutes. The resulting solution is diluted with water and. extracted with ether. The ethereal extract is washed with dilute hydrochloric acid, dilute 50- dium carbonate, and finally with Water. The ether extract is then evaporated to small volume, and petroleum ether is added thereto to produce crystals of 3(a) ,21-diacetoxy-11,20-diketo-pregnane (compound 23); M. P. IOU-110 (3., which contain 10% of solvent of crystallization, Recrystallization of this material from benzenepetroleum ether gives a product having a dec. point of 82-90 C.

About 3.0 g. of said 3(a) ,21-diacetoxy-1L20-diketo-pregnane is dissolved in a mixture of 30 cc. of alcohol and 11.4 cc. of acetic acid, and the resulting solution is cooled to 0 C. and treated with about 10.6 g. of potassium cyanide. The mixture is stirred for about one-half hour, and then permitted to warm to room temperature. After two hours, the solution is diluted with Water, and the crystalline precipitate thus obtained is filtered and Washed. The wet cake is dissolved in ethyl acetate, excess water removed,

and the solution is evaporated to small volume in tion is acidified with acetic acid, the benzene is evaporated in vacuo, and the residual material crystallized from dilute methanol to produce 1.45

g. of crude product; M. P. 242-254 C. This malterial is further purified by recrystallization from acetone and from dilute alcohol to produce substantially pure A -3(c) ,21-dihydroxy-11-keto-20- cyano-pregnene (compound 25); M. P, 256-257 This product is treated with excess acetic anhydride and pyridine, at room temperature, to produce substantially pure A (a),21-diacetoxy- 11-keto-20-cyano-pregnene (compound 26).

Various changes and modifications may be made in my invention as described without departing from the spirit and scope thereof. To the extent that these changes and modifications are Within the purview of the annexed claims, they are to be considered as part of my invention.

I claim:

1. The process which comprises reacting 3(a) hydroxy-21-acetoxy-1L20-diketo-pregnane with hydrogencyanideand reacting the cyanhydrin thus obtained with chromic acid followed by phosphorus oxychloride in the presence of pyridine to produce A -3,1l-diketo-20-cyano-2lacetoxy-pregnene.

2. The process of preparing a A -20-cyanopregnene compound having at least one nuclear keto substituent which comprises reacting hydrogen cyanide with a 20-keto-pregnane compound containing at least one nuclear hydroxy substituent, reacting the cyanhydrin thus obtained with an oxidizing agent thereby oxidizing said nuclear hydroxy substituent to a keto radical, and reacting the resulting nuclear ketosubstituted 20-hydroxy-20-cyano-pregnane com pound with a dehydrating agent.

9 3. The process which comprises reacting hy drogen cyanide with a compound of the formula:

CHzR

droxy 11,20 diketo-pregnane with hydrogen cyanide, reacting the cyanhydrin thus obtained with chromic acid thereby oxidizing the nuclear hydroxy substituent to a keto radical, and reacting the resulting 3,11-diketo-20-hydroXy-20- cyano-pregnane with phosphorus oxychloride in the presence of pyridine to produce A -3,11-diketo-ZO-cyano-pregnene.

5. The process of preparing A -3,11-diketo-20 cyano-2l-hydroxy-pregnene which comprises reacting 3(a)-hydroxy-21- acetoxy-11,20-diketopregnane with hydrogen cyanide, reacting the cyanhydrin thus obtained with chromic acid thereby oxidizing the nuclear hydroxy substituent to a keto radical, and reacting the resulting 3,11- diketo-20-hydroxy-20-cyano-21 acetoxy preg nane with phosphorus oxychloride in the presence of pyridine followed by methanolic potassium hydroxide.

LEWIS HASTINGS SARET'I'.

No references cited. 

4. THE PROCESS WHICH COMPRISES REACTING 3-HYDROXY - 11,20 - DIKETO-PREGNANE WITH HYDROGEN CYANIDE, REACTING THE CYANHYDRIN THUS OBTAINED WITH CHROMIC ACID THEREBY OXIDIZING THE NUCLEAR HYDROXY SUBSTITUENT TO A KETO RADICAL, AND REACTING THE RESULTING 3,11-DIKETO-20-HYDROXY-20CYANO-PREGNANE WITH PHOSPHORUS OXYCHLORIDE IN THE PRESENCE OF PYRIDINE TO PRODUCE $17-3,11-DIKETO-20-CYANO-PREGNENE. 